Even outdoorsy types can find something useful in the App Store. There are apps for astronomers, fitness buffs, hikers, skiiers and more. The guys at The Adventure Life have picked 25 of the best.

And the best part is that the vast majority of these apps are free or very inexpensive. To be honest, I'm actually surprised at how much cool stuff is out there. I mean, I didn't know there was an app focused specifically on knot tying. There is even a kayaking version that incluedes 11,000 stream-flow gauges across the United States (you might want to invest in a heavy-duty waterproof case for that one). [The Adventure Life]